The goal of this project is to summarize, evaluate, and interpret data contained in the NTP rodent carcinogenicity database and other large databases. As the NTP carcinogenicity database becomes increasingly accessible to the general scientific community, there is increased opportunity for inadvertent misuse of the database by those who may not have a complete understanding of the complex information it contains. We demonstrated that a previously published evaluation of the NTP database exaggerated the frequencies of statistically significant decreasing tumor trends, The factors contributing to these errors included failure to adjust for survival differences, evaluating improper tumor combinations, failure to achieve the reported (p<0.01) level of significance, double counting a chemical's site-specific decreased tumor incidence, and using scientifically inadequate studies. In another project, we evaluated the large database of results from the Frog Embryo Teratogenesis Assay - Xenopus (FETAX), as part of an ICCVAM (Interagency Coordinating Committee on the Validation of Alternative Methods) initiative, We found that in some cases there was significant inter-laboratory variability in the reported malformation rates that appeared to be related to diagnostic differences among investigators, Based on these results, specific recommendations were made as to how the FETAX protocols could be improved to reduce this variability and facilitate any future validation of this assay.